1. Field of the Invention
The present invention relates to a 2D/3D switchable display apparatus, and more particularly, to a highly efficient 2D/3D switchable display apparatus having improved brightness by enhancing a light use efficiency.
2. Description of the Related Art
A stereo image display providing a stereo image is greatly needed in a variety of fields such as medical images, games, advertisements, education, and military affairs. Also, as high resolution TVs are becoming popular, stereo TVs that can display stereo images are expected to be popular in the future.
In general, a stereo image display apparatus provides an image for the left eye and an image for the right eye having a binocular parallax respectively to the left eye and the right eye of a user. The user recognizes the left eye image and the right eye image provided by the stereo image display apparatus through the retinas of both eyes so as to view a 3D stereo image. The stereo image display apparatus includes a parallax barrier type and a lenticular type.
According to the parallax barrier type, image to be seen by the left and right eyes are alternately displayed in a vertical pattern and then the images are viewed using thin vertical strips, that is, a barrier. For example, as shown in FIG. 1, a stereo image display apparatus of the parallax barrier type includes a backlight unit 11, an LCD panel 13, and a parallax barrier 12 having an opening 12a and a barrier 12b which are arranged at a predetermined period. Although in FIG. 1 the parallax barrier 12 is arranged between the LCD panel 13 and the backlight unit 11, the parallax barrier 12 can be arranged in front of the LCD panel 13. In this structure, the images for the left and right eyes alternately displayed by the LCD panel 13 can be separated by the opening 12a of the parallax barrier 12.
However, in the above-described parallax barrier type stereo image display apparatus, since part of the light provided by the backlight unit 11 is blocked by the barrier 12b, a light use efficiency is low and brightness is decreased. Furthermore, for the stereo image display apparatus, since the left eye image and the right eye image are simultaneously displayed from the LCD panel 13, the resolution of a stereo image that is viewed by the user is reduced to ½ of the original resolution of the LCD panel 13. When a multi-viewpoint stereo image, for example, a three viewpoint or more stereo image, is provided, the resolution is reduced as much.
Also, to provide a 2D image or 3D image according to an image signal to be displayed, a stereo image display needs a switching operation between a 2D image mode and a 3D image mode.
To prevent the reduction of brightness, as shown in FIG. 2, a method has been suggested in which a reflection film 14 is coated on the surface of the barrier 12b facing the backlight unit 11 and a reflection panel 15 is installed on the lower surface of the backlight unit 11. In this case, the light emitted from the backlight unit 11 and incident on the barrier 12b can be reused because the light is reflected by the reflection film 14 and then reflected again by the reflection panel 15. In this case, however, there still remains a problem that resolution is reduced and that the switching between 2D and 3D is not possible.